Patent GB-631587-A (GB)
Title: Improvements in or relating to radio tracking systems
IPC: G01S13/66
Filed: 1943-07-29
Abstract: 631,587. Radiolocation; pulse and sawtooth circuits. SPERRY GYROSCOPE CO., Inc. July 29, 1943, No. 12366. Convention date, July 30, 1942. [Classes 40 (vi) and 40 (vii)] In a radiolocation system in which pulses reflected from a distant object are separated from extraneous disturbances by passage through a pulse gate, under the control of local synchronous pulses, phase agreement between the reflected and local pulses is indicated by magnifying a part of the time-scale of a cathoderay tube to which the received pulses are applied and adjusting the phase of the local pulses until the reflected pulses occupy the magnified part of the scale. To avoid the loss of illumination which would normally result from such magnification, a potential is applied to the intensity-controlling grid of the cathoderay tube to make the illumination uniform over the whole scale or even greater at the magnified part. An automatic volume-control for the incoming reflected pulses is derived from the output side of the pulse gate to render such control independent of extraneous disturbances. The system may be used for aligning a gun, searchlight, &c. on a target. Certain features of the system described form the subject-matter of Specifications 631,588 and 631,589. General operation, Fig. 1. Pulses from a generator 4 under the control of a control oscillator 1 are sent out from a transmitter 6 connected over a wave-guide to a radiator 7 having a radiation pattern 8, Fig. 2. Reflected pulses are received by a receiving structure 9 of the kind described in Specification 579,763 and involving a reflector 11, and a wave-guide 12 with a rotatory offse't termination 13, the whole providing a reception pattern 14, Fig. 2, rotating round the central axis 16. The received pulses pass through a mixer 18, intermediate-frequency amplifier 21 and second detector 23 to the pulse-gate 33. An automatic volume control potential derived from the output side of the pulse gate is applied over lead 73 to the amplifier 21. The pulse-gate is also fed with pulses generated by a range pulse generator 34 under control of oscillator 1, the phase of these local pulses being manually adjustable by a member 37 until they are in phase with the reflected pulses at which time the pulse-gate opens to pass on the pulses to circuit 63. A cathode-ray tube 27 is used to indicate such phase synchronism, the reflected pulses being supplied to one pair of deflecting plates 26 and a sweep voltage providing for magnification of one part of the time-scale being supplied to the other pair of plates 28. Intensifier 30 providing a potential for the intensitycontrolling grid 25 of tube 27 causes illumination at the magnified part to be normal or increased. When phase synchronism has been effected, the setting of member 37 or the scale on tube 27 7 provides an indication of the distance of the reflecting object. To align the apparatus in the exact direction of the object, the pulses from the pulse-gate are fed to azimuth and elevation phase detectors 106, 107, which are also fed with reference voltages, displaced 90 degrees in phase, generated by a two-phase generator 101 driven by motor 17. If a distant object observed on indicator 27 is in, say, direction 15, Fig. 2, the intensity of the receiver pulses will be subjected to a modulation at the frequency of rotation of structure 9. The phase detectors 106, 107 produce potentials corresponding to the difference in phase between such pulse modulation and the reference voltages to control cathode-ray indicators 108, 109, and the main axis 16 is then adjusted in azimuth and elevation to coincide with direction 15 as indicated by zero deflection in the indicators. Pulse-gate 33, Fig. 4. Valves 46, 51 are connected in parallel between a fairly high negative source 47 and a common output resistance 48 which is also connected to the grid of a third valve 56. Valves 46, 51 are normally conducting and the current in resistance 48 biasses tube 56 to complete cut-off. Received pulses and local pulses from range pulse generator 34 are applied to valves 46, 51, respectively, but tube 56 is only able to pass current when such pulses are received simultaneously, i.e. when the reflected and local pulses (adjusted by member 37) are in phase. Automatic volume-control circuit 22, Fig. 4. The output circuit of the pulse gate is connected through a rectifier 66 to the grid of a valve 67 7 connected in series with a resistance 68 and a second valve 69. Any change in intensity of the received pulses varies the current in resistance 68 and changes the bias over lead 72 on the grid of tube 69. This control is effective in the opposite sense to restore equilibrium in the circuit but the voltage on the cathode of tube 69 is changed and this voltage is connected over lead 73 to the screen-grids of the intermediate frequency amplifier 21. Range sweep circuit 29, Fig. 4. A control valve 82 in series with a pentode 76 is fed over circuit 77 with square waves from generator 2, Fig. 1, controlled by oscillator 1. During positive half-cycles of the square wave, condenser 87 is charged over tube 82, and during the succeeding negative half-cycle discharges through pentode 76. The control grid of the pentode is fed with the local pulses from range pulse generator 34 so that for the duration of each pulse the pentode becomes of lower resistance causing condenser 87 to discharge more rapidly. The voltage on condenser 87 is applied over lead 91 as a sweep voltage for cathode-ray indicator 27 so that over part of the scale, Fig. 5, a magnified image 31<1> is produced. The operator adjusts member 37 until the image of the reflected pulses remains in magnified condition whilst other disturbances such as 32<1> are unmagnified, and this condition indicates phase agreement between the reflected and local pulses. Intensifier 30, Fig. 4. The sweep voltage on lead 91 is differentiated by condenser 121 and resistance 122 giving a voltage having a constant low value during periods 96, 98, Fig. 5, and a constant higher value during the magnification period 97. This voltage may be directly applied to the intensity-control grid 25 of indicator tube 27 to maintain the brightness constant over the whole scale. To further increase the intensity over the magnified part 97, the voltage from resistance 122 is applied to one amplifier tube 123 and local pulses from generator 34 are fed to a second amplifier 127. The voltage due to the resultant current in common resistance 126 is applied to grid 25.